Dehydration, particularly from gastroenteritis or other illnesses that causes vomiting, diarrhea and fever (e.g. pyloric stenosis, thyrotoxicosis, diabetes insipidus, cystic fibrosis, bowel ischemia, etc.), is a common pediatric complaint. According to the Centers for Disease Control and Prevention, for children younger than 5 years, the annual incidence of diarrheal illness is approximately 1.5 billion, while deaths are estimated at between 1.5 and 2.5 million per year. Furthermore, there is substantial evidence to show that aging causes changes in body water composition, and that renal function and thirst perception on average decline among older adults. These three factors account for the prevalence of dehydration among the older adult population. In a study, dehydration was diagnosed in 6.7% of hospitalized patients aged 65 and over. Furthermore, 1.4% of the patients had dehydration as the principal diagnosis. Prospective studies in long-term care facilities (LTCs) showed that residents were dehydrated in 50% of the febrile episodes and that 27% of the LTC resident population referred to hospitals was admitted due to dehydration.
Dehydration is not only a common but also a very serious condition in older adults. The mortality of elderly patients with dehydration is high if not treated adequately and in some studies exceeds 50%. In terms of morbidity, several studies showed an association between high degrees of dehydration and poor mental function. Further, it was found that dehydration was a significant risk factor for developing thrombo-embolic complications, infectious diseases, kidney stones, and obstipation.
Although dehydration is almost always avoidable it is often not identified quickly enough in the hospital or primary care environment. While individuals who are able to manage their own fluid intake are also considered to be at risk, the elderly and young children are often most vulnerable. For the elderly this is often due to reduced renal function, decreased thirst sensation and increased susceptibility to long-term conditions such as diabetes. For pediatric populations this is because infants and children are very susceptible to volume depletion since they have higher body water content relative to adults, along with higher metabolic rates and increased body surface area to mass index, which means that they require proportionally greater volumes of water than adults in order to maintain their fluid equilibrium.
The clinical assessment of dehydration is difficult and highly subjective. Common features of dehydration are dry mouth, dry and dark colored tongue, increased pulse rate, weak pulse pressure and strength, increased breathing rate, elevated body temperature (i.e. fever), lateral furrowing and cracking of the tongue, and indentation of the teeth on the gums. In addition, in infants and young children other subjective signs including eye appearance, fontanel (soft spot) appearance, activity level and skin turgor are also routinely used in the diagnosis of dehydration.
As a result of the difficulty in reliably assessing the range of clinically relevant physiological signs of dehydration owing to the high degree of subjectivity required, there is a significant need for an objective measure of the hydration status of an individual, especially from elderly and pediatric population groups, which is reliable, easy to use and clinically relevant.
Testing or monitoring of dehydration status in very young and old patients is a difficult and complex issue for health workers. When not diagnosed in time, dehydration can have a profound effect on the health of patients in the form of malnutrition, renal failure, liver failure, deep vein thrombosis. Sometimes these effects can be fatal. Total body water and serum osmolality measurements are the well accepted techniques for measuring dehydration levels, but are both invasive and time consuming.
In US 2007/0048224 A1 a hydration sensor or sensing element configured to measure the hydration level of a user is disclosed. The sensing element can include a water-permeable material positioned in between two water-impermeable materials. The sensing element can be coupled to a bottle of fluid, or a carrier with a timer. The sensing element can be incorporated into a handheld device. The sensing element can be a disposable element, an element applicable for more than one-time use, or a re-usable element. The sensing element or sensor can be calibrated for a specific user or a group of users. One or more additional sensors that do not measure hydration level of the user can be coupled to a hydration sensing element to determine the amount of fluid consumption for the user in different conditions.
In WO 2009/027898 A1 a method and apparatses for measuring skin properties are disclosed. To improve the accuracy of detection of the dehydration level, an apparatus is presented that comprises: a positioning unit configured to position the apparatus over the piece of skin; a laser sensor configured to measure the distance between the laser sensor and the piece of skin by utilizing the self-mixing technology; wherein the positioning unit is further configured to generate a negative pressure on the piece of skin so as to raise the surface of the piece of skin, and position the laser sensor at a pre-determined location.
However, there is still a need for practical, user-friendly and reliable detection and early warning of dehydration.